1. Field of the Invention
The present invention relates in general to an improved aircraft structure, and more particularly to subdermally-reinforced elastomeric transitions for sealing apertures or gaps.
2. Description of the Prior Art
Modem aircraft have both external aerodynamic control surfaces and a number of exterior access panels such as for weapons bay, landing gears, and avionics access. These panels, or doors, are typically fabricated from a variety of metallic and composite materials to reduce weight. The control surfaces and doors form discontinuous gaps or apertures with aircraft skin elements that are located adjacent to the control surfaces and doors, such as at hinge lines. Aperture windows and maintenance access panels also form gaps with the aircraft skin.
All gaps on an aircraft must be sealed to reduce aerodynamic drag and turbulence and to prevent dirt and contaminants from entering the aircraft. In military applications, the gaps must also be sealed to eliminate gaps between surfaces and reduce electromagnetic emissions, both of which contribute to the radar signature of aircraft. Also, the seal for gaps requires time-consuming and costly maintenance. Hence, there is a need to reduce or minimize the running length of gaps on the aircraft to reduce aerodynamic drag and radar cross-section during flight as well as to reduce maintenance time on the ground. Further, there is a need to reduce or minimize the number of gaps for moveable aircraft members, such as doors, preferably to at least one gap for such members.
Elastomeric transition panels are used to seal gaps or apertures between various moveable aircraft members such as access doors, access panels and aperture windows. There are dimensional changes in the size and shape of the doors which, in turn, cause dimensional changes in the gaps, due to the large strains and temperature variations modem aircraft encounter during flight. Strains on the order of 20% to 30% may be encountered for door hinge lines and bay doors. Elastomeric transition panels are designed to be elastic to adjust to these strain-induced and thermal-induced dimensional changes.
Elastomeric transition panels are often reinforced to impart improved flexural strength while preserving high in-plane strain capacity. A prior art elastomeric transition panel, continuous moldline technology (CMT), is disclosed in U.S. Pat. No. 5,222,699 to Albach, et al. In the CMT panel, a reinforcement member is encapsulated within a thick solid elastomeric block, the size of the reinforcement member determining the thickness of the elastomeric block. As a result, the CMT panel is heavy and difficult to actuate when used in CMT airframe applications. Also, the CMT panel is labor-intensive to manufacture and maintain and is often short-lived and unreliable during service. There is a need for a lightweight, reinforced, elastomeric transition panel having a substantially thin elastomeric section with improved flexural strength and high strain capacity. Also, such a panel is needed which may be subdermally reinforced and which may incorporate flexible cores.
A subdermally-reinforced elastomeric transition is provided in which an elastomeric skin is attached to a plurality of subdermal supporting members that engage subdermal reinforcing members. The reinforcing members may be rods or support rails which the supporting members engage. The supporting members may be attached to the elastomeric skin in an orientation that is perpendicular to a direction of strain of the skin and may have a plurality of holes or slots for receiving the reinforcing members. Alternatively, the supporting members may be oriented to be parallel to the direction of strain of the skin, the reinforcing members being located substantially within the supporting members.